function max()
{
	if [ $# -ne 3 ];then
		echo "usage:max p1 p2 p3"
		return 1
	fi
	max=$1
	if [ $max -lt $2 ];then
		max=$2
	fi
	if [ $max -lt $3 ];then
		max=$3
	fi
	return $max
}
max 1 2 3 
echo "the max number of 1 2 3 is : $?"
exit
